Assembly for adjusting mobile elements of furniture

ABSTRACT

The invention relates to an assembly for adjusting mobile elements of furniture, comprising a motor, a control circuit which is provided with push-button switches, a current supply circuit, a mains connection, a mains supply circuit, a mains isolating relay and an auxiliary current source. The aim of the invention is to construct said assembly in a more cost-effective manner whilst at the same time retaining a safety isolation from the mains. To achieve this, the first push-button switch forms a direct electric circuit with the motor and the control input of the isolating relay is connected in parallel to the motor, or is connected to the latter via a Graetz bridge.

[0001] The invention relates to an assembly for adjusting mobileelements of furniture, with a motor displaying a first and a secondconnection, a control circuit for controlling the motor, which isprovided with at least a first push-button switch for controlling themotor, a power supply circuit with an operating voltage output, with amains connection located between a mains plug that can be connected toan alternating-current mains and the power supply circuit, with a relaydisplaying a relay switch and a control input controlling the relayswitch, where the relay switch is located in the mains connection and isin OFF position when unexcited, and with an auxiliary power source thatcan be connected to the control input of the relay.

[0002] An assembly of the kind mentioned above is known from EuropeanPatent Specification 0 615 667 B1. The assembly described therein forsafety isolation of control devices from the mains refers to an assemblyfor adjusting mobile elements of furniture that is provided with twomotors. One motor displays a first and a second connection. Furthermore,a control circuit comprising a first and a second push-button switch isprovided for each motor. The control circuit of a motor also includes afirst and a second relay. The relay coil of the first relay is connectedto operating potential via the first push-button switch and the relaycoil of the second relay via the second push-button switch. The relayswitches of both relays are designed as changeover switches, where onechangeover contact is connected to the operating voltage output of theone polarity and the other changeover contact with the operating voltageoutput of the other polarity. The centre contact of the relay switch ofthe first relay is connected to the first connection of the motor andthe centre contact of the relay switch of the second relay to the secondconnection of the motor. In unexcited state, the relay switches eachestablish a connection between their centre contact and the operatingvoltage output with the same polarity as on the respective other relayswitch.

[0003] In this known assembly, the operating voltage source is designedas a direct-current source and each motor as a direct-current motor. Asa result, the design of the control circuit provides control of thedirection of the motors. If, for example, the first push-button switchis operated, the first relay picks up and switches over the relayswitch. While the first and second connection of the motor had the samepotential up to that time, the switching operation now connects thefirst connection to the other operating voltage potential. The motorthereupon performs motion in one direction until the first push-buttonswitch is released. If the second push-button switch is subsequentlyoperated, the second relay picks up, thereby reversing the polarity onthe motor and causing the motor to move in the other direction.

[0004] In this known assembly, there is also a third relay with a relayswitch located in the mains lead to the power supply circuit. Anauxiliary power source is connected in parallel to the operating voltageoutput of the power supply circuit. This auxiliary power source isconnected to the control input of the third relay via each of thepush-button switches.

[0005] Since the relay switch of the third relay is in OFF position whenunexcited, the power supply circuit is initially isolated from themains. If one of the push-button switches is now operated, the voltageof the auxiliary power source is applied to the control input of thethird relay via the push-button. This relay picks up as a result andswitches its relay switch to the ON position. The power supply circuitis thereby connected to the mains voltage and supplies an operatingvoltage at its operating-voltage output. As a result, each of the relaysforming part of the control circuit can pick up, provided the associatedpush-button switch is pressed. The motor thereupon performs itsadjusting motion. The third relay remains operational during this time,since its control input is now supplied with operating voltage. If thepush-button switch is released, for instance because the necessaryadjusting motion has been completed, the relay associated with therespective push-button drops off, as does the third relay, and thecircuit arrangement is once again isolated from the mains.

[0006] The disadvantage of this arrangement is that each push-buttonswitch has to be provided with a relay, meaning that the circuitarrangement not only requires a considerable amount of space, but isalso complex and expensive to manufacture.

[0007] Consequently, the object of the invention is to disclose anassembly for adjusting mobile elements of furniture that can beconstructed more easily and cost-effectively while maintaining safetyisolation from the mains, i.e. isolation from the mains during timeswhen no control functions have to be executed and connection to themains when control commands are received.

[0008] According to the invention, this object is solved in that thefirst push-button switch forms an electric circuit with the motor andthe operating voltage output. Moreover, either the control input of themains isolating relay is connected in parallel to the motor, or arectifier bridge known as a Graetz bridge is connected between the motorand the control input of the mains isolating relay. A rectifier bridgeof this kind is provided with four diodes, of which two first diodeshave their cathodes interconnected in a positive node, while theiranodes are each interconnected with the cathodes of the two seconddiodes in an alternating-current node. In this context, the first andsecond connections of the motor are each connected to analternating-current node. The positive and negative nodes are eachconnected to the control input of the mains isolating relay.

[0009] The first alternative provides for the simplest realisation ofthe solution according to the invention, where both the motor and themains isolating relay are connected directly by the first push-button.In this context, the relay switch of the mains isolating relay is in OFFposition when in quiescent state. Consequently, the power supply circuitis not connected to the mains. If the first push-button is pressed inorder to start the motor, the voltage from the auxiliary power source isapplied via the first push-button switch to the mains isolating relay,which picks up and connects the power supply circuit to the mains.Operating voltage is then present at the operating-voltage output andthe mains isolating relay is held in picked-up state by the operatingvoltage for as long as the first push-button switch is pressed. When itis released, the voltage at the control input of the mains isolatingrelay is interrupted and this mains isolating relay drops off. The powersupply circuit is then no longer connected to the mains, since the relayswitch of the mains isolating relay is once again in OFF position.

[0010] The second alternative of the solution according to the inventiondisplays the same mode of operation. When the push-button switch ispressed, the voltage from the auxiliary power source is applied to thecontrol input of the mains isolating relay via the rectifier bridge,causing the mains isolating relay to pick up and connect the powersupply circuit to the mains for as long as the push-button switch ispressed. However, interconnection of the rectifier bridge avoidsfeedback from the control input of the mains isolating relay to themotor connections. This permits the use of several motors, for example,all of which operate with one mains isolating relay, as described inmore detail below.

[0011] In one embodiment of the invention, provision is made for theoperating-voltage output to be designed as a DC output and the motor asa DC motor.

[0012] Designing the invention with DC motors offers not only favourabletorque distribution, but also the advantage of simple control of thesense of rotation of the motors.

[0013] Especially for simple control of the sense of rotation of the DCmotors, a further embodiment of the invention provides for the inclusionof a second push-button switch and for both the first and the secondpush-button switch to be designed as changeover switches. One of theirchangeover contacts is connected to the operating-voltage output of theone polarity, while the other changeover contact is connected to theoperating voltage of the other polarity. The centre contact of the firstpush-button switch is connected to the first connection of the motor,and the centre contact of the second push-button switch is connected tothe second connection of the motor. When not operated, each push-buttonswitch displays a connection between its centre contact and theoperating-voltage output with the same polarity as the other push-buttonswitch.

[0014] This arrangement makes it possible to cause the motor to rotatein one direction with the first push-button switch and in the otherdirection with the second push-button switch. In this context, eitherone push-button switch or the other must be operated in order to obtainrotation. Simultaneous operation would not, however, be dangerous. Itwould merely not cause any movement of the motor.

[0015] In another embodiment of the invention, there is provision forthe motor assembly, comprising the motor and the first or the first andsecond push-button switch, to be present at least in duplicate. In thiscontext, each motor assembly can be provided with a mains isolatingrelay, the control input of which is connected in parallel to theassociated motor, while the relay switches of all mains isolating relaysare connected in parallel to each other. Alternatively, each motorassembly can be provided with a rectifier bridge, thealternating-current node of which is connected to the connections of therespective motor and whose positive and negative nodes are each jointlyconnected to the control input of one and the same mains isolatingrelay.

[0016] This embodiment makes it possible to use several motors that canbe controlled directly by one control circuit, meaning that aninterconnected relay is avoided while preserving the possibility ofsafety isolation from the mains. When a motor is switched on, operatingvoltage is present between its first and second connections. If severalmotors were then connected to one and the same mains isolating relay,the connection of the mains isolating relay in parallel to the motorswould cause the operating voltage to cross from the activated motor tothe others. This is prevented either by the rectifier bridge connectedbetween each motor and the one mains isolating relay, or by installingseveral, separate mains isolating relays.

[0017] In another embodiment of the invention, there is provision forthe auxiliary power source to consist of an alternating-current source.In this context, it is conceivable for an auxiliary transformer to beprovided, the secondary output of which is connected in parallel to theoperating-voltage output of the power supply circuit. This provides analternating voltage as the auxiliary power for switching on the mainsisolating relay.

[0018] This kind of application of an auxiliary alternating voltage isconceivable both in an embodiment using AC voltage as the operatingvoltage and AC motors, and when using DC voltage as the operatingvoltage. In the latter case, either the AC voltage from the auxiliarypower source could be rectified, or the auxiliary power source coulddisplay such a high internal resistance that DC components are notdestroyed or switch off the auxiliary power source as soon as the mainsisolating relay has picked up, for which purpose a separate relay switchcan be provided, for example.

[0019] However, it must be noted that there is no complete safetyisolation from the mains in this context, since the auxiliary powersource remains connected to the mains as a power source in the circuitarrangement.

[0020] In a more favourable embodiment of the invention, the auxiliarypower source consists of a direct-current source. In principle, it ispossible for the direct-current source to again be designed with a mainsconnection, for instance using a transformer and a downstream rectifiercircuit. Expediently, however, the direct-current source can also bedesigned as a direct-current source that is electrically isolated fromthe mains.

[0021] In one embodiment of the invention, this is realised in that theauxiliary power source consists of a capacitor. Capacitors withrelatively low leakage currents are expediently used for this purpose inorder to retain an existing charge for an acceptable period of time. Asa general rule, assemblies according to the invention are operated atleast once over a period of one week. This period will suffice tomaintain the capacitor charge.

[0022] In the event that longer periods of non-use of the assemblyaccording to the invention have to be bridged, operating reliability canbe increased by providing a manual operating device on the relay contactof the mains isolating relay.

[0023] Another possibility for reliably maintaining the charge of thecapacitor as the auxiliary power source is to provide a trigger circuithaving a pulse output that is additionally connected to the mainsisolating relay. This trigger circuit intermittently switches the mainsisolating relay, as a result of which the power supply circuit brieflysupplies operating voltage at its operating-voltage output, thuscharging the capacitor back up to operating voltage potential. Theinterval between pulses is governed by the leakage current of thecapacitor, making it possible also to use relatively inexpensivecapacitors, which usually also have relatively high leakage currents.Even if a pulse interval of several minutes were to be selected, theinfluence of the alternating-current mains, which is essentially to beavoided by safety isolation from the mains, would be completelynegligible.

[0024] Another embodiment of the auxiliary power source as adirect-current source consists in the auxiliary power source comprisinga battery. Since batteries can have service lives of more than a year,especially if they are used only very rarely, as in the case inquestion, a battery ensures operational readiness at all times. Absentoperational readiness in the event of a drained battery can be preventedby means of a regular maintenance cycle of the assembly according to theinvention.

[0025] In a particularly favourable embodiment of the invention,provision is made for the mains isolating relay to display a secondrelay switch or, in the event of there being several mains isolatingrelays, for each mains isolating relay to display a second relay switchand for each of these relay switches to be located in a separate line ofthe mains connection.

[0026] This embodiment implements bipolar disconnection of the mainslead. This means that the downstream arrangement can be shielded notonly from alternating electromagnetic fields, but also alternatingelectrical fields.

[0027] The invention is explained in more detail below on the basis of apractical example.

[0028] The associated figures show the following:

[0029]FIG. 1 An assembly according to the invention with one motor,

[0030]FIG. 2 An assembly according to the invention with an additional,pulse-switched mains isolating relay,

[0031]FIG. 3 An assembly with two motors, each of which is decoupled viaa rectifier bridge,

[0032]FIG. 4 An assembly according to the invention with three motors,each of which is decoupled via a rectifier bridge,

[0033]FIG. 5 An assembly according to the invention with three motors,each of which is assigned a mains isolating relay.

[0034] The assembly shown in FIG. 1 is equipped with a first motor 1.This first motor 1 has a first connection 2 and a second connection 3.Also provided is a control circuit 4, which is equipped with a firstpush-button switch 5 and a second push-button switch 6. A power supplycircuit 7 comprises a transformer 8 and a rectifier circuit 9. Thedirect-current output of rectifier circuit 9 simultaneously representsoperating-voltage output 10 of power supply circuit 7. The assembly isfurther provided with a mains connection 11, which is located between amains plug 12 that can be connected to an alternating-current mains (notshown in detail) and power supply circuit 7.

[0035] A mains isolating relay 13 is provided for disconnecting mainsconnection 11 between mains plug 12 and power supply circuit 7. Thismains isolating relay 13 displays a first relay switch 14 and a secondrelay switch 15. These relay switches 14 and 15 are each located in aline of mains connection 11. When mains isolating relay 13 is unexcited,i.e. in the state where the relay coil of the mains isolating relay isnot receiving power, they are in OFF position, i.e. they are open anddisconnect the mains lead. Also provided is an auxiliary power source16, which is connected in parallel to operating-voltage output 10.

[0036] First push-button switch 5 and second push-button switch 6 forman electric circuit together with motor 1 and operating-voltage output10. First push-button switch 5 and second push-button switch 6 are eachdesigned as changeover switches. One of their changeover contacts 17 isconnected to the operating-voltage output with positive (+) polarity,while the other changeover contact 18 is connected to theoperating-voltage output with negative (−) polarity. Centre contact 19of first push-button switch 5 is connected to first connection 2 ofmotor 1. Centre contact 20 of second push-button switch 6 is connectedto second connection 3 of motor 1. In this context, each push-buttonswitch 5 and 6 is configured in such a way that, when not operated, itmakes a connection between its centre contact 19 or 20 and theoperating-voltage output 10 with positive (+) polarity.

[0037] As illustrated in FIG. 1, the control input of mains isolatingrelay 13 is connected in parallel to motor 1.

[0038] If first push-button switch 5 is now operated, for example, theparallel connection of motor 1 and mains isolating relay 13 results inthe voltage from auxiliary power source 16 being applied to the coil ofmains isolating relay 13. Mains isolating relay 13 thereupon operatesfirst relay switch 14 and second relay switch 15, which thus move intoON position and connect the mains lead to power supply circuit 7, i.e.particularly with the primary side of transformer 8. Operating voltageis thereupon supplied at operating-voltage output 10 of power supplycircuit 7, as a result of which operating potential is applied to motor1 which can consequently move. This happens for as long as firstpush-button switch 5 is pressed, in which context the movement of motor1 can also be limited by a limit switch (not shown) . As soon as firstpush-button switch 5 is released, it returns to its original startingposition, as a result of which positive potential is again applied tofirst connection 2 of motor 1, just as to second connection 3 of motor1. Motor 1 comes to a halt due to the absence of a potential difference.

[0039] The same procedure takes place when second push-button switch 6is pressed, the only difference being that first motor 1 experiences areversal of polarity between its first connection 2 and its secondconnection 3, this bringing about a reversal of the sense of rotation ofmotor 1.

[0040] As in FIG. 1, auxiliary power source 16 in FIG. 2 again consistsof battery 21 with capacitor 22 connected in parallel. This parallelconnection means that an auxiliary voltage with a low internalresistance is constantly supplied, thereby achieving a rapid response ofthe mains isolating relay. Although battery 21 keeps capacitor 22 in aconstant charge state, which is additionally constantly refreshed byoperating-voltage output 10, it may happen in the worst case thatbattery 21 is drained and the entire circuit arrangement has not beenoperated for such a long time that the leakage current of capacitor 22has discharged the latter. To also prevent this occurrence, a triggercircuit 23 is provided, the pulse output of which is additionallyconnected to the control input of mains isolating relay 13. This triggercircuit 23 intermittently switches on mains isolating relay 13, meaningthat operating-voltage output 10 supplies operating voltage for theduration of the pulse, this recharging capacitor 22. Although theassembly is not isolated from the mains during the occurrence of thepulse from trigger circuit 23, this happens so rarely and for such ashort period of time that the influence of the alternating-current mainscan be completely neglected.

[0041] In the embodiment illustrated in FIG. 3, a second motor 2 isarranged alongside first motor 1. Like first motor 1, this second motor2 is also provided with a control circuit 4, which in turn comprises afirst push-button switch 5 and a second push-button switch 6.

[0042] In this circuit arrangement, mains isolating relay 13 is nolonger connected directly in parallel to motor 1 or second motor 24.Instead, a rectifier circuit 25 known as a Graetz bridge is connectedbetween them. This is done in such a way that first connection 2 andsecond connection 3 of motor 1 are connected to the alternating-currentnode. The negative and the positive node of rectifier circuit 25 areconnected to the control input of mains isolating relay 13. A rectifiercircuit 25 is also connected to second motor 24 and mains isolatingrelay 13 in the same way. The effect of rectifier circuits 25 is thatthe application of operating voltage to first motor 1 has no influenceon second motor 24 and vice versa. In other words, the motors aredecoupled from each other by rectifier circuits 25, although theapplication of operating voltage between their first connection 2 andtheir second connection 3 always results in mains isolating relay 13picking up.

[0043] As illustrated in FIG. 4, the circuit arrangement according toFIG. 3 can also be expanded to include a third motor 26 and furthermotors not shown in the drawing.

[0044] Another possibility for using several motors 1, 24 and 26 isillustrated in FIG. 5. In this circuit arrangement, the rectifiercircuit 25 for each motor is eliminated. Instead, in addition to mainsisolating relay 13 provided for motor 1, there is a mains isolatingrelay 27 for second motor 24 and a mains isolating relay 28 for thirdmotor 26. Thus, each motor has its “own” mains isolating relay. The modeof operation is in each case the same as that illustrated in FIG. 1. Tothis end, the respective relay switches 14 and 15 of mains isolatingrelays 13, 27 and 28 are connected in parallel to each other. As aresult, every application of operating voltage to one of motors 1, 24and 26 causes one of mains isolating relays 13, 27 and 28 to pick up,while the parallel connection of relay switches 14 and 15 means that thealternating mains voltage is always connected through to power supplycircuit 7.

List of Reference Numbers

[0045]1. First motor

[0046]2. First connection

[0047]3. Second connection

[0048]4. Control circuit

[0049]5. First push-button switch

[0050]6. Second push-button switch

[0051]7. Power supply circuit

[0052]8. Transformer

[0053]9. Rectifier circuit

[0054]10. Operating-voltage output

[0055]11. Mains connection

[0056]12. Mains plug

[0057]13. Mains isolating relay

[0058]14. First relay switch

[0059]15. Second relay switch

[0060]16. Auxiliary power source

[0061]17. Changeover contact

[0062]18. Changeover contact

[0063]19. Centre contact of the first push-button switch

[0064]20. Centre contact of the second push-button switch

[0065]21. Battery

[0066]22. Capacitor

[0067]23. Trigger circuit

[0068]24. Second motor

[0069]25. Rectifier bridge

[0070]26. Third motor

[0071]27. Mains isolating relay

[0072]28. Mains isolating relay

1. Assembly for adjusting mobile elements of furniture, with a motordisplaying a first and a second connection, a control circuit forcontrolling the motor, which is provided with at least a firstpush-button switch for controlling the motor, a power supply circuitwith an operating voltage output, a mains connection located between amains plug that can be connected to an alternating-current mains and thepower supply circuit, a mains isolating relay displaying a relay switchand a control input controlling the relay switch, where the relay switchis located in the mains connection and is in OFF position whenunexcited, and an auxiliary power source that is connected in parallelto the operating-voltage output, characterised in that the firstpush-button switch (5) forms an electric circuit with the motor (1) andthe operating voltage output (10) and either the control input of themains isolating relay (13) is connected in parallel to the motor (1) ora rectifier bridge (25), known as a Graetz bridge, which has fourdiodes, of which two first diodes have their cathodes interconnected ina positive node, while their anodes are each interconnected with thecathodes of the two second diodes in an alternating-current node and thecathodes of the two second diodes are interconnected in a positive node,and where one alternating-current node each is connected to the firstand second connection of the motor and the positive and negative nodeare each connected to the control input of the mains isolating relay(13).
 2. Assembly according to claim 1, characterised in that theoperating-voltage output (10) is designed as a DC output and the motor(1) as a DC motor.
 3. Assembly according to claim 2, characterised inthat a second push-button switch (6) is provided and in that the first(5) and the second push-button switch (6) are designed as changeoverswitches, one of whose changeover contacts (17) is connected to theoperating-voltage output (10) of the one polarity, while the otherchangeover contact (18) is connected to the operating voltage output(10) of the other polarity and the centre contact (19) of the firstpush-button switch (5) is connected to the first connection (2) of themotor (1) and the centre contact (20) of the second push-button switch(6) is connected to the second connection (3) of the motor (1) and, whennot operated, each push-button switch (5; 6) switch displays aconnection between its centre contact (19; 20) and the operating-voltageoutput (10) with the same polarity as the other push-button switch (6;5).
 4. Assembly according to one of claims 1 to 3, charact erised inthat the motor assembly, comprising the motor (1) and the first (5) orthe first (5) and second push-button switch (6), is present at least induplicate, where either each motor assembly is provided with a mainsisolating relay (13; 27; 28), the control input of which is connected inparallel to the associated motor (1; 24; 26), while the relay switchesof all mains isolating relays (13; 27; 28) are connected in parallel toeach other, or each motor assembly is provided with a rectifier bridge(25), the alternating-current node of which is connected to theconnections of the respective motor and whose positive and negativenodes are each jointly connected to the control input of one and thesame mains isolating relay (13).
 5. Assembly according to one of claims1 to 4, characterised in that the auxiliary power source (16) consistsof an alternating-current source.
 6. Assembly according to claim 5,characterised in that the auxiliary power source (16) consists of amains transformer connected to the alternating-current mains. 7.Assembly according to one of claims 1 to 4, characterised in that theauxiliary power source (16) consists of a direct-current source. 8.Assembly according to claim 7, characterised in that the auxiliary powersource (16) consists of a capacitor (22).
 9. Assembly according to claim8, characterised in that a manual operating device is provided on therelay switch (14; 15) of the mains isolating relay (13).
 10. Assemblyaccording to claim 8, characterised in that a trigger circuit (23) isprovided having a pulse output that is additionally connected to themains isolating relay (13).
 11. Assembly according to claim 7,characterised in that the auxiliary power source (16) consists of abattery (21).
 12. Assembly according to one of claims 1 to 11,characterised in that the mains isolating relay (13; 27; 28) displays asecond relay switch (15), or the mains isolating relays each display asecond relay switch (15) and in that each relay switch (14; 15) islocated in a separate line of the mains connection (11).